1. Field of the Invention
The present invention relates to a process for separating phosphate minerals from a phosphate ore, especially from a phosphate-carbonate ore, by flotation in the presence of a collector agent.
2. Description of the Prior Art
In the art, a large number of processes and compounds are known for seclective froth-flotation of phosphate minerals from ores which contain phosphate. One such process is presented in Finnish Patent Application No. 811333, wherein an anionic collector agent, usually a fatty acid, is first added to an aqueous slurry of the ore or of its concentrate, whereafter the slurry is subjected to flotation in order to remove a silicate-containing waste from the concentrate. Next the slurry is treated with an alkali in order to remove the collector-agent covers from the mineral surfaces, and finally the combined concentrate is floated by using a cationic collector agent, especially an amine-type collector agent, the pH being neutral or mildly acidic, in order that the phosphate concentrate be separated in as pure a form as possible.
From Finnish Patent Application No. 790725 there is also known an amphoteric surface-active agent to be used as a collector agent. Such an agent has been obtained, for example, by allowing a suitable amino compound, e.g. methyl alanine or methyl glycine, to react with an epoxy or chlorohydrin compound. In order to obtain the best result, the hydrophilic and hydrophobic portions of the collector agent can, in this as in other known amphoteric agents, be varied by adjusting the length of the carbon chain and, for example, the number of ether bonds.
Furthermore, from Finnish Patent Application No. 783804 there is known a collector agent composition which is based on a monoester of sulfosuccinic acid and a fatty acid based on a vegetable or animal oil, the contents of the constituents in the composition ranging from 1-99% to 99-1%, calculated according to weight.
At present, fatty acids are perhaps the most commonly used collector agents. The fatty acids may be unsaturated or, for example, technical fatty acid compositions. There are also other compounds among the proposed collector agents, such as alkyl benzene sulfonate, alkyl sulfate, and amines.
In order to enchance the selectivity of the separation of phosphate and carbonate minerals, and in order to improve the yield, various regulating chemicals are often also used in flotation. By using additives it is often also possible to decrease the total consumption of chemicals and/or the costs. Generally known regulating chemicals include waterglass, corn starch, gum arabic, carboxymethylcellulose, neutral oil, carbon or sulfur dioxide gas, and various emulsifiers and frothers. The known processes and chemicals have the disadvantage that the grade of the phosphate concentrate usually remains low when the aim is a high recovery, especially as carbonate minerals float along with phosphates.